There are many applications, such as ducting systems and housings in gas turbine engines, where it is essential or desirable to affect sealing between annular components that are at variable axial distances from one another due to manufacturing tolerances on several components in the assembly and thermal expansion and contraction during operation of the engine. Typically, metallic, resilient sealing rings are used to seal against opposed axially or radially facing surfaces in the annulus between two concentric pipes or in opposed axially facing surfaces at the interface of two aligned pipes to confine high temperature and pressure fluids located in the pipes.
While there are numerous sealing rings known in the art for confining fluids at high temperatures and pressures, they have various disadvantages. For example, some of these sealing rings cannot vary substantially in length and others loose their resiliency after a limited number of pressure and thermal deflection cycles. In addition, many of these sealing rings are affected by the high pressures they experience and become unbalanced and therefore subject to leakage. Other seals cannot provide sealing against axially facing but radially offset surfaces and some seals can only accommodate compressive deflection by the bending of their cross sections and not by torsional deflection, i.e., twisting, of the cross section. Finally, many of these prior sealing rings are formed from very thin metal and therefore tend to dent during manufacture, handling and assembly.
Examples of these prior sealing rings are disclosed in the following U.S. Pat. Nos. 3,285,632 to Dunkle; 3,575,432 to Taylor; 3,797,836 to Halling; 3,857,572 to Taylor et al; 3,869,132 to Taylor et al; 4,121,843 to Halling; and 4,457,523 to Halling et al.
Thus, there is a continuing need for improvement in metallic sealing rings for use at high temperatures and pressures which are subject to large axial variations and repeated pressure and thermal deflection cycles.